CIV3294: Structural Design
Introduction to Steel Design, Section Classification and Bending Capacity
Question 1
Draw the shear force diagram and bending moment diagram for the beam shown below. The
reaction forces are known: RAY = 16.1 kN, RAM = 0, RBY = 78.5 kN, RBM = 0, RCY = 55.4 kN,
RCM = 71.4 kNm (clockwise).
100 kN
10 kN/m
A
C
B
5m
2.5 m
2.5 m
Question 2
a) Calculate the following properties of cold-formed rectangular hollow section (RHS)
150 x 50 x 2 about the major axis: Second moment of area (Ix), elastic section modulus
(Zx) and plastic section modulus (Sx) and shape factor.
b) Calculate the following properties of cold-formed rectangular hollow section (RHS)
150 x 50 x 2 about the minor axis: Second moment of area (Iy), elastic section modulus
(Zy) and plastic section modulus (Sy) and shape factor.
c) Compare the results in a) and those in b), and comment on the difference.
d) Compare the results obtained in a) and b) with those published by the manufacturer,
and explain the reason for the difference.
e) Calculate the bending stress at top of the section subject to a sagging moment of 5 kNm
about the major axis. Calculate the bending stress at a location 30mm below the neutral
axis. Indicate whether they are compressive or tensile.
Question 3
Calculate the effective section modulus Ze of the section and hence the section moment
capacity φMs of the following section made of Grade 300, heavily-welded plates.
12
140
360
12
410
140
10
All dimensions in mm
Department of Civil Engineering, Monash University
Edition Date: 3/2023
CIV3294: Structural Design
Introduction to Steel Design, Section Classification and Bending Capacity
Question 4
Complete the table below for the steel sections shown. All sections are bending about their
horizontal axis.
e
(show calculations)
Section
bf
Location
ep
ey
sp=
sy=
sp=
sy=
Flange
tf
d
tw
bf = 800 mm
tf = 20 mm
d = 1440 mm
tw = 16 mm
Web
Grade 300,
welded plates
heavily
s =
bf
Whole
section
Flange
tf
d
tw
Web
bf = 800 mm
tf = 20 mm
d = 1420 mm
tw = 16 mm
Grade 300, heavily
welded plates
s =
Whole
section
Department of Civil Engineering, Monash University
Edition Date: 3/2023
Slenderness
of element
CIV3294: Structural Design
Introduction to Steel Design, Section Classification and Bending Capacity
Solution for Q1:
SFD
BMD
Solution for Q2:
a) Ix = Iouter – Iinner = (14.06 – 11.93) × 106 = 2.13 × 106 mm4, Zx = Ix/(D/2) = 28.44 × 103 mm3,
Sx = Souter – Sinner = (281.25 – 245.13) × 103 = 36.12 × 103 mm3, Shape Factor = Sx/Zx =
1.27
b) Iy = Iouter – Iinner = (1.56 – 1.18) × 106 = 0.38 x 106 mm4, Zy = Iy/(D/2) = 15.13 × 103 mm3,
Sy = Souter – Sinner = (93.75 – 77.23) × 103 = 16.52 × 103 mm3, Shape Factor = Sx/Zx = 1.09
c) Roughly Ix = 5.6 Iy, Zx and Sx are roughly about twice as Zy and Zy, Shape Factor for the
major axis is 16% larger.
d) Calculated Ix and Zx are about 2.6% larger than those in the table. Sx is about 1.7% large
than that in the table. Iy and Zy are about 1.7% larger than those in the table. Sy is about 1.3%
larger than that in the table. Reason: corners are not considered.
e) Bending stress at top = Mx/Zx = 176 MPa (in compression), bending stress at 30mm below
NA = 70 MPa (in tension).
Department of Civil Engineering, Monash University
Edition Date: 3/2023
CIV3294: Structural Design
Introduction to Steel Design, Section Classification and Bending Capacity
Solution for Q3:
Department of Civil Engineering, Monash University
Edition Date: 3/2023
CIV3294: Structural Design
Introduction to Steel Design, Section Classification and Bending Capacity
Solution for Q4:
Department of Civil Engineering, Monash University
Edition Date: 3/2023